The invention relates to centrifugal separators, and in particular to improvements in vertical centrifugal separators which extend the useful life of the screen of the separator, thereby reducing downtime of a separator and decreasing its maintenance.
As is well-known, centrifugal separators are widely used in a variety of processes in which material separation is required. Typically, material is fed into a top of the separator and is brought into contact with rotating elements within the separator. Solid material is retained near the center of the separator; while, free liquids are slung off, by centrifugal force, to the outside of the separator. These liquids are then directed to a drain outlet, and the solid material falls, by gravity, to the bottom of the separator from whence it is discharged and collected.
Because of the abrasive quality of the material fed into a separator, and the impact forces which are created as the material is moved through it, components within the separator are subject to reasonably rapid wear. Screens, rotors, etc., all need to be replaced with such frequency, that a separator has a substantial downtime, when necessary maintenance is being performed.
The maintenance problem with centrifugal separators has long been recognized and different measures have been undertaken to address it. In U.S. Pat. No. 4,961,722, for example, a screen assembly is described having separate upper and lower portions. In conventional separators, the screen projects as far upwardly within the separator housing as a flight assembly of the separator. In use, material introduced into the separator is flung against the screen by centrifugal forces. Because of the impact forces of material against the screen, the upper portion of the screen rapidly becomes tom and needs frequent replacement. The separator disclosed in the above noted patent facilitates replacement of the upper part of the screen, where most of the wear occurs, allowing the lower portion of the screen assembly to be used for a longer period of time.
In U.S. Pat. No. 5,256,289, which is incorporated herein by reference, a centrifugal separator is disclosed which includes a pocket assembly below the inlet to the separator and above the screen. The material to be separated is initially flung against the inner surfaces of this pocket assembly, rather than against the screen, to protect the screen from these initial impacts. The material then falls, by gravity, from the pocket into the screen area of the separator where separation occurs. Because the pocket bears the brunt of the initial impact, this separator reduces the wear on the screen assembly, extending the useful life of the screen assembly. Although this separator works well, there are other methods that could be used to help protect and extend the life of the screen assembly of the separator.